The present invention generally relates to the field of aircraft navigation, and particularly to a split PPS/SPS architecture for military aircraft flying in civilian airspace.
Emerging Global Air Traffic Management (GATM) and Joint Precision Approach and Landing System (JPALS) requirements continue to drive military aircraft toward a need for civil interoperability when engaged in flight in the national airspace. However, this interoperability cannot compromise the performance of military aircraft systems when in a tactical environment. Military aircraft are increasingly being required to show xe2x80x9ccivil interoperabilityxe2x80x9d up to, and including Federal Aviation Administration (FAA)/civil aviation authority (CAA) certification of onboard equipment, including GPS equipment.
The tremendous growth in air traffic presents increasing challenges for air traffic service providers, air carriers, and the military. Such growth is straining airspace capacity and airport resources. The air traffic system requires significant upgrades to increase system capacity and flight efficiency while continuing to meet flight safety standards. The International Civil Aviation Organization (ICAO), Federal Aviation Administration (FAA), and other civil aviation authorities (CAA) plan to implement a new air traffic architecture to meet this need. This new architecture takes advantage of emerging technologies in communication, navigation, and surveillance to improve air traffic management.
The current plan is to implement a new air traffic environment to culminate in 2010 with the attainment of dynamic routing, commonly referred to in the U.S. as xe2x80x9cfree flight.xe2x80x9d Dynamic routing gives operators the freedom to choose their own routes, speeds, and altitudes, in real-time, thus providing visual flight rules (VFR) flexibility with instrument flight rules (IFR) protection and separation and a shift from air traffic control (ATC) to air traffic management (ATM). The civil aviation community refers to these changes as Communication, Navigation, Surveillance/Air Traffic Management (CNS/ATM). Due to the major impact to Department of Defense global operations, these new concepts will be referred to as Global Air Traffic Management (GATM).
The ability to reduce aircraft separations and implement other new air traffic management (ATM) procedures while maintaining or improving safety standards is based on the use of new technology. The most critical technology elements of the new Communication, Navigation, Surveillance/Air Traffic Management (CNS/ATM) environment are satellite-based navigation, increased use of data links rather than voice for pilot/controller communication in oceanic/remote airspace as well as en-route and terminal environments, and improved surveillance that will enhance both ground and cockpit situational awareness. If aircraft are not equipped with the appropriate new technologies, they will not be able to operate in airspace where new separation standards and ATM procedures are implemented by civil aviation authorities, and will therefore be excluded from that airspace. For Department of Defense aircraft to operate in this new environment, significant modifications to existing aircraft must be accomplished.
One element of the GATM problem is Satellite based navigation or GPS. Implementation of GPS in all military aircraft is now mandated by 2005. To meet this mandate, military aircraft system program offices (SPOs) integrated P(Y) code GPS in three basic configurations: stand-alone receiver 3A, Miniature Airborne GPS Receiver (MAGR), cargo utility GPS receiver (CUGR), integrated with a flight management system (FMS) CDNU GPS Embedded Module (CGEM), or embedded/integrated with an inertial (GPS Embedded Module (GEM)), or GRAM.
Historically, the military and the civilian market follow different paths to certify their systems for flight. The FAA/CAA drives a process intensive, regimented development process to ensure a receiver meets the technical standard order (TSO) for flight critical systems. The military also follows a regimented development process; however, to date most military systems are not required to meet the FAA/CAA guidelines. Instead, the military self-certifies their systems as meeting the needs for flight in civil airspace.
To meet the emerging GATM requirements, the military market encourages the use of commercially available aviation equipment. However, military and civil markets have diverging requirements. For the civilian market, Local Area Augmentation System (LAAS), Wide-Area Augmentation System (WAAS) and the new civil frequency are the near term driving requirements. In the military market, Wide-Area Augmentation System (WAAS), Joint Precision Approach and Landing System (JPALS), the new military M-Code Signal (Lm), selective availability anti-spoofing module (SAASM) and navigation warfare (NAVWAR) anti-jamming (AJ) enhancements are driving requirements. This divergence in driving requirements is causing a debate over the best way to pre-position aircraft for flight in civil airspace and address the concerns to meet the divergent civil and military needs.
The first part of the controversy is the use of precise encrypted P(Y) code GPS in civil airspace. P(Y) GPS is designed to meet the rigorous needs of the tactical military environment. Unfortunately, the drive for military use complicates and diverges from the goals of a civil certified GPS receiver. PPS receivers utilize L1 and L2 to calculate the GPS position and perform ionosphere corrections. L1 is a protected frequency for safety of flight operations, but L2 is not. Therefore, in order for the PPS receiver to operate in the civil airspace, the receiver must be capable of excluding L2 from the solution.
A second issue is the certification of PPS receivers by foreign CAA. The current generation of PPS receiver has classified software that is not accessible for inspection by foreign governments (the exception is Category A and B memorandum of understanding (MOU) countries). Since every foreign government retains the right to approve aviation equipment for flight in their sovereign airspace, they need to be able to inspect the software operating within the GPS receiver. To utilize a PPS receiver, the military would require a country-by-country waiver or agreement to allow the use of a PPS receiver within their airspace. This is further complicated with the incorporation of Selective Availability Anti-Spoofing Module (SAASM) since no foreign government has access to the classified algorithms within the Selective Availability Anti-Spoofing Module (SAASM).
Finally, a technical standard order (TSO) does not exist for a PPS receiver. While a manufacturer may claim some level of TSO or TSO equivalency, the fact remains that a TSO has not been written for PPS receivers and therefore the PPS portion of a receiver can not be TSO""d. In addition, it is unlikely that a TSO will be developed in the near future because of the issues presented previously.
Therefore, it would be desirable to provide a navigation system that is suitable for certification by civil aviation authorities (CAA) yet still provide the tactical environment capability (high anti-jam, anti-spoof) required for military needs.
Accordingly, the present invention is directed to a split PPS/SPS architecture for military aircraft flying in civilian airspace. To satisfy disparate Civil and Military aviation requirements, separate GPS receivers will satisfy the operational need of the Military User and the certification requirements of the Civil Aviation Authorities (CAA) at a lower life cycle cost than an approach to meet both requirements in a single receiver.
In a first aspect of the present invention, a navigation system suitable for use in civilian airspace, includes a first precise positioning service (PPS) global positioning system (GPS) receiver in a first line replaceable unit (LRU). A second standard positioning service (SPS) global positioning system (GPS) receiver in a second line replaceable unit (LRU) is also included. The second standard positioning service (SPS) global positioning system (GPS) receiver in the second line replaceable unit (LRU) is suitable for at least one of certification, upgrade and replacement independent of the first precise positioning service (PPS) global positioning system (GPS) receiver in the first line replaceable unit (LRU).
In a second aspect of the present invention, a vehicle including a navigation system includes a first precise positioning service (PPS) global positioning system (GPS) receiver in a first line replaceable unit (LRU). A second standard positioning service (SPS) global positioning system (GPS) receiver in a second line replaceable unit (LRU) is also included. The second standard positioning service (SPS) global positioning system (GPS) receiver in the second line replaceable unit (LRU) is suitable for at least one of certification, upgrade and replacement independent of the first precise positioning service (PPS) global positioning system (GPS) receiver in the first line replaceable unit (LRU).
In a third aspect of the present invention, a navigation system suitable for use in civilian airspace, includes a first precise positioning service (PPS) global positioning system (GPS) receiver in a first line replaceable unit (LRU). A second standard positioning service (SPS) global positioning system (GPS) receiver in a second line replaceable unit (LRU) is also included. The second standard positioning service (SPS) global positioning system (GPS) receiver in the second line replaceable unit (LRU) is certified under a technical standard order corresponding to operation utilizing a standard positioning service and is suitable for at least one of certification, upgrade and replacement independent of the first precise positioning service (PPS) global positioning system (GPS) receiver in the first line replaceable unit (LRU).
In a fourth aspect of the present invention, a navigation system suitable for use in civilian airspace includes a line replaceable unit (LRU). A first precise positioning service (PPS) global positioning system (GPS) receiver and a second standard positioning service (SPS) global positioning system (GPS) receiver are included with the line replaceable unit (LRU). The second standard positioning service (SPS) global positioning system (GPS) receiver is suitable for at least one of certification, upgrade and replacement independent of the first precise positioning service (PPS) global positioning system (GPS).
It is to be understood that both the forgoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and together with the general description, serve to explain the principles of the invention.